Diaphragm elements



June 26, 1956 c. R. SMiTH 2,751,935

DIAPHRAGM ELEMENTS Filed Dec. 13, 1954 United States Patent F DIAPi-BZAGM ELEDEENTS Charles R. Smith, Mequon, Wis., assignor to Cutler, er, Inc., Milwaukee, Wis, a corporation of Dela= ware Application December 13, 1954, Serial No. 474,952

9 Claims. (Cl. 137--795) This invention relates to pressure responsive diaphragm elements.

A primary object of the invention is to provide a diaphragm the expansion of which is substantially linear over a wide range of pressures uniformly applied thereto.

Another object is to provide a diaphragm which is pressure-linear over a wide range of applied pressures, which expands relatively greatly in respect to its diameter and which will withstand a large number of expansions without breaking.

A more specific object is to provide a self-loaded diaphragm which is pressure-linear over the range of domestic refrigerator power element operation and, in addition, is a size, durability, and cost commensurate with the requirement of domestic refrigeration service.

In the interval between manufacture of a refrigerator and the time when it is placed in service, the refrigerator, and its power element, may be transported and stored in places where temperature differentials are greater than those which the power element will experience during normal service. Accordingly self-loaded diaphragms which form a part of those power elements must be able to withstand greater pressure differentials than those to which they are subjected during normal service. Another object of the invention is to provide a diaphragm which can withstand such extreme pressure variations without loss of calibration in its normal operating range.

Other objects and advantages of the invention will hereinafter appear.

One embodiment of the invention is shown in the accompanying drawing, it being understood that certain modifications may be made in the embodiment illustrated and that other modifications are possible to be made without departing from the spirit of the invention or the scope of the appended claims.

In the drawings, Figure 1 is a top plan view of a diaphragm embodying the invention,

Fig. 2 is an enlarged sectional view taken on line 22 of Fig. l, and

Fig. 3 is a chart of certain of the structural features of the corrugations of the diaphragm greatiy exaggerated.

Referring to Figs. 1 and 2, the diaphragm there shown comprises a circular cup 16 the bottom wall of which is provided with a series of concentric corrugations and a central boss 12.

To facilitate description, that face of the diaphragm which is seen in Fig. 1 and which is seen from the top in Fig. 2 will be referred to as the top or upper side. The opposite side will be referred to as the bottom or lower side. Each corrugation will be considered as including that portion of the bottom of the cup which extends between successive low points. Thus, in Fig. 2, corrugation 14 extends from point 17 to point 18, corrugation 15 extends from point 18 to point 19 and corrugation 16 extends from point 19 to point 20. The uppermost or top points of corrugations 14, 15 and 16 are designated 21, 22 and 23, respectively. The outer side walls of corrugations 14, 15 and 16 are numbered 24, 25 and 26,

2,751,935 Patented June 26, 1956 ice respectively, and their inner side walls are numbered 27, 28 and 29, respectively. The construction line 30 lies in the axis of the diaphragm. Other unnumbered construction lines indicate the slopes of the sides of the corrugations. The numeral 31 designates the outer side wall of the diaphragm.

When assembled in a power element, the upper surface of the diaphragm is normally subjected to atmospheric pressure and the bottom surface is subjected to a pressure which is a function of some quantity to be measured.

The spacing between corresponding points of successive inner corrugations tends to decrease. Thus the distance between points 22 and 23 is less than the distance between points 21 and 22. Also, the distance between points 18 and 1 is less than the distance between points 17 and 18 and is greater than the distance between points 1*) and 20.

The amplitude or the height of the respective sides of any corrugation, measured in a direction parallel to the axis of the diaphragm from the bottom points to the top point, need not be the same. The height of the outer sides of the corrugations tends to increase in successive outer corrugations whereas the height of the inner sides of the corrugations tends to increase in successive inner corrugations. Thus the spacing, in a direction parallel to axis 30, between points 13 and 22 is less than that between points 17 and 21 and greater than that between points 19 and 23. Similarly the spacing, thu measured, between points 22 and 19 is lessthan that between points 21 and 18 and is greater than that between points 23 and 2h. The slope of the outer sides of the corrugations tends to decrease in successive inner corrugations but the slope of the inner sides of the corrugations tends to increase in successive inner corrugations.

In addition, successive inner corrugations tend to be positioned downwardly so that the corrugated portion of the diaphragm, when relaxed, is funnel shaped or bell shaped as indicated by construction line a and [9V drawn through the mid-points of the corrugations in Figs. 2 and 3, respectively. It will be apparent that at different ambient pressure differentials on opposite sides of the diaphragm that the diaphragm may or may not be funnel or bell shaped.

In the chart, Fig. 3, the numerals 17' through 30' correspond to numerals 17 through 39 in Fig. 2. This chart does not iilustrate a diaphragm but is intended to show, in exaggerated form, the relationships between the sides and the top and bottom points of a diaphragm embodying the invention.

The various structural features hereinbefore described contribute to make the diaphragm substantially pressurelinear over a wide range of applied pressures. Pressurelinearity is defined as the characteristic of expansion of the diaphragm along its axis as a linear function of the differential of pressure uniformly applied on opposite sides of the diaphragm.

It is apparent that certain of these structural features determine others of them so that the shape of the diaphragm may be defined as various combinations of these features. Accordingly, description of the effects of the various structural features on diaphragm performance, which efiects are themselves complex, is complicated by the fact that the features may be described in different combinations.

in general, substantial pressure-linearity is achieved by varying the heights of the inner and outer sides of the corrugations as described or by varying the slopes of said sides as described. The change in corrugation width and amplitude, as described, has the eflfect of increasing, to higher applied pressures, the range of pressures over relatively small.

which the diaphragm is pressure-linear for a given diaphragm sensitivity. Conversely, in a diaphragm of given sensitivity, substantial pressure-linearity is provided over a given range with less variation in corrugation slope and height if the change in width is increased.

Shaping the diaphragm to be somewhat funnel or bell shaped'in its relaxed condition permits increased diaphragm expansion with a of expansion and stress in the individual corrugations.

Substantial pressure-linearity over a specified range may be achieved by various combinations of the degree in which particular ones of these structural features are present in the diaphragm shape. The dominant feature may diifer in different combinations.

The number of corrugations in a diaphragm and the thickness and resilience of the diaphragm material are major factors in determining its sensitivity or ratio of incremental expansion to incremental change in pressure differential.

The dimensional changes in successive corrugations are small in small diaphragms of'the type described. Accordingly, tools for making such diaphragms must be accurately made. However, it is a feature of the invention that the amplitude of the corrugations may be made This reduces the need for accuracy in the tools and simplifies problems attendant upon deep drawing of the diaphragm material. It has been found that minor deviations in individual corrugations from the 7 crease in successive inner corrugations.

2. The diaphragm defined in claim 1 in which the crosssectional width decreases in successive inner corrugations.

3. The diaphragm defined in claim 2 in which corresponding points of successive inner corrugations define a funnel or bell shape when said diaphragm is relaxed.

4. A pressure responsive diaphragm having formed therein a series of concentric corrugations, the slopes of the inner sides of which increase and the slopes of the outer sides of which decrease in successive inner corru gations for substantially linear expansion of said diaphragm in response to equal increments of pressure change over a given range of pressure uniformly applied thereto.

5. A pressure responsive diaphragm having formed therein a series of concentric corrugations the slopes of the inner sides of which increase in successive inner corrugations and the slopes of the outer sides of which decrease in successive inner corrugations and in which the cross-sectional width of successive inner corrugations is decreased for substantially linear expansion of said diaphragm in response to equal increments of change over a given range of pressure uniformly applied thereto.

6. The diaphragm defined in claim 5 in which the amplitude of the inner side of said corrugations increases in successive inner corrugations for substantially linear expansion of said diaphragm over an increased range of pressures.

7. The diaphragm defined in claim 5 in which corresponding points of successive inner corrugations define a funnel or bell shape when said diaphragm is relaxed.

8. A pressure responsive diaphragm having formed therein a series of concentric corrugations the slopes and the heights of the inner sides of which increase in successive inner corrugations and the slopes and the heights of the outer sides of which decrease in successive inner corrugations for substantially linear expansion of said diaphragm in response to equal increments of change over a given range of pressure uniformly applied thereto.

9. The diaphragm defined in claim 8 in which the crosssectional width of the corrugations decreases in succes sive inner corrugations for substantially linear expansion of said diaphragm over an increased range of pressures.

References Cited in the file of this patent UNITED STATES PATENTS 1,927,617 Schmidt Sept. 19, 1933 2,111,168 Chansor Mar. 15, 1938 FOREIGN PATENTS 847,073 Germany Aug. 27, 1952 

